The Center for Structural Biology at the University of Illinois at Chicago (UIC) proposes acquisition of a Beckman Coulter XL-I analytical ultracentrifuge, with accessories, including the newly-available Fluorescence Detection System from Aviv Biomedical, to advance the research of five NIH-funded research groups, all of which involve the study of protein interactions with other proteins or ligands.The equipment will be housed in the Center for Structural Biology in a shared equipment room. The primary users belong to three departments (Biochemistry, Center for Pharmaceutical Biotechnology, and the Center for Molecular Biology of Oral Disease) in three colleges (Medicine, Pharmacy and Dentistry) of the university. The equipment will complement currently available shared instrumentation that includes ultra high field NMR, fluorescence, and CD spectrometers and DSC and ITC calorimeters by enabling quantitative examination of the solution interactions of proteins of interest with other proteins and ligands, irrespective of whether there are spectroscopic changes or measurable enthalpy changes in the interactions. Fluorescence detection capabilities will significantly extent the capabilities of the XL-I in terms of the range of systems that can be examined, including range of dissociation constants that can be measured, the complexity of systems analyzable, and sample sparing. Systems that will be studied include (i) viral envelope proteins gp41 and gp120 from HIV and the S1 and S2 from SARS coronavirus (Caffrey), (ii) interactions of the LDL receptor related protein with its chaperone RAP and with serpin-proteinase ligands, and characterization of domain-domain interactions in the human pan-proteinase inhibitor alpha-2-macroglobulin (Gettins), (iii) protein-protein interactions in the regulation of pro-drug processing enzymes, and in the role of scaffold proteins in organizing multiple partners at specific cellular sites (Lavie), (iv) heterogeneous interactions in the antioxidant response, the oligomerization state of class 3 deacetylases, of Bacillus anthracis metabolic pathway enzymes, and of proteases from the SARS coronavirus that will be targeted for inhibition by development of novel protease inhibitors (Mesecar) and (v) conformational changes in antithrombin in the antiangiogenic forms, organization of crmA-caspase complexes, and studies on the complex formed between ZPI, protein Z and factor Xa that permits inhibition of factor Xa by ZPI (Olson). The research to be carried out using this equipment addresses basic questions of the structure and function of proteins that are involved in human viral infections such as HIV or SARS, or normal physiological processes such as blood coagulation. The knowledge gained will be invaluable for design of therapeutics against such infections or in amelioration of diseases associated with aberrant functioning of processes such as blood coagulation. [unreadable] [unreadable] [unreadable]